Aircraft are designed to operate at varied pressure conditions. When an aircraft is on the ground (or during takeoff, before it reaches flight altitude), pressure inside the aircraft cabin (cabin pressure) is generally equal to the pressure outside the aircraft cabin (environment pressure). During aircraft operation flight conditions, the cabin is pressurized with an overpressure compared to the outside environment. This regulated and controlled overpressure inside the cabin produces a difference in pressure (a “differential pressure”) between inside the aircraft cabin and the outside atmosphere. The cabin pressure is higher than the environment pressure. This differential pressure can be used to generate a vacuum pressure on-board an aircraft for various functions.
For example, the differential pressure can be used to create a vacuum used for vacuum toilet operations. In other instances, the differential pressure can be used to drain one or more waste water systems of the aircraft. As background, grey waste water is often generated on board an aircraft. This water includes water or other liquids from sinks and sumps, generated in various aircraft modules such as galleys, lavatories, or any other locations on board an aircraft where water or other liquids can collect or drain. These systems are often connected to a drain mast, which leads to the outside environment. The drain mast releases the liquids to the external environment.
Because these systems are connected to the outside environment, without a valve or other air/water management system that interfaces between the system and the outside environment, the differential pressure would cause air leakage to occur. Air leakage also creates undesirable noise within the cabin. Accordingly, air stop valves have been used at the interface between the sink or sump and the drain mast in order to prevent these problems from occurring. These air stop valves typically use an internal membrane or disc to operate. In order to overcome the pressure differential and to force the membrane open and closed, a water column is required. The water column helps create a force that can cause opening of the membrane or disc. As illustrated by prior art FIG. 13, a pressure difference pulls a piston down with a force relative to the pressure difference. The water pressure of the column creates and opposite force which opens the membrane of the valve. The water pressure is created by an increase in the water level such that a higher pressure difference requires a larger water column. One downside of these current systems is that they require the presence of the water column, which requires additional installation height and space, as well as additional hoses in order to operate. In certain instances, the required installation height is not available. Accordingly, improved waste water air stop valves are thus desirable.